This invention relates to an open end spinning rotor for a spinning machine, which rotor has a self-cleaning capability.
As is known, the rotor for an open end spinning machine is generally provided with an annular wall surface which extends from the rim of an open end of the rotor radially outwardly from the rotary axis and downwards to a region of maximum diameter, where a fibre collecting surface is formed into which the fibres are collected. Open end spinning machines employing the abovementioned rotors are broadly in use for the mass production of yarn and are highly required to be capable of continuous high speed spinning operation for a long duration. However, the spinning rotors in the open end spinning machine are in fact supplied with separated fibres, which more or less contain a certain amount of small impurities, such as, dust, husks and the like. Even if such impurities entering the spinning rotor with the fibres are rolled in the yarn, there will be no influence upon the yarn quality, because critical impurities such as causing yarn breakage have been removed before entering the spinning rotor. However, the spinning rotor faces a serious problem which must be settled in order to allow it to continuously operate at a high speed for a long duration.
In the open end spinning machine, since the fibres are fed into the spinning rotor in the separated or opened state, the impurities mixed with the fibres can move under conditions such that they are substantially released from restriction by the separated fibres. The impurities once separated from the fibres are difficult to re-mix with the fibres which have been deposited in the fibre collecting region of the spinning rotor in the form of a sliver or fibre ring, because of the differences in properties and configuration between the impurities and fibres. That is, the impurities generally have a greater mass than the fibres and therefore they are caused to move into the fibre collecting groove by the action of centrifugal force, which is stronger than that applied to the fibers, with the result that the impurities are deposited and accumulated in the region of maximum diameter or narrowest portion of the fibre collecting groove, while the fibres are positioned on the inner side of the impurities, i.e., on the side adjacent to the rotation axis of spinning rotor. Therefore, when the fibres are removed by twisting them into a tail end of a yarn, it is difficult to cause the impurities on the outer side to be rolled into the twisted yarn, especially where the impurities resemble a cubic shape. The impurities thus remaining in the region of maximum diameter of the fibre collecting groove are compressed by the strong action of centrifugal force and gradually develop into a layer of deposition having a considerable thickness during a long duration of the spinning operation, causing the radius of the maximum diameter region to become larger than the initial most favourable radius. The fibre ring in the fibre collecting groove becomes expanded in width and is subject to a smaller twisting action. This seriously affects the spun yarn so as to invite yarn irregularities, smaller yarn twist and decreased yarn strength, resulting in a poor yarn quality. It is of course essential for the high speed open end spinning operation to apply a sufficient twisting action to the fibre ring and therefore a loss of twist due to the deposition of the impurities makes it difficult to carry out the high speed spinning.
In order to allow the continuous high speed spinning operation for a long duration without causing a quality reduction, it is understood from the foregoing that the impurities must be prevented from being deposited and accumulated in the maximum diameter region on the outer side of the fibre ring.
In view of the above, Japanese patent specification No. 52-12292 teaches to form a fibre sliding wall surface of the spinning rotor, along which fibres slide to the maximum diameter region, so as to have a stepped portion with the aim of causing the impurities to be forcibly separated from the sliding down fibres at the stepped portion and to be fed into an inner region in front of the ring of fibres collected in the fibre collecting groove. Such a spinning rotor somewhat exhibits an impurity rolling-in function, although not sufficient.
With consideration for these circumstances, the inventor of the present invention has sought and found factors causing the impurities once separated from the supplied fibres to be sufficiently rolled into the ring of fibres in the fibre collecting groove.
The first factor is to cause the impurities once separated at the stepped portion of the fibre sliding wall surface to directly adhere to and/or move closely adjacent to the inner side of the fibre ring. The second factor is that even the impurities carried onto the outer side of the fibre ring, i.e., the maximum diameter region are to be rolled into the fibre ring. The last factor is to cause micro-impurities, which stall before abutting against the fibre sliding wall surface and deposit on the bottom of the spinning rotor, to directly adhere to and/or move closely adjacent to the inner side of the fibre ring.
Various designs of a spinning rotor have higherto been proposed to prevent the impurity accumulation. However, none of the prior art spinning rotors have been designed with due consideration for the abovementioned factors, and they do not exhibit a sufficient self-cleaning capability.
It is accordingly a principal object of the present invention to provide an open end rotor for a spinning machine, which is free from an accumulation of impurities in a fibre collecting region of the spinning rotor to allow a continuous high speed spinning operation for a long duration without a yarn quality reduction.